Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
  • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
  • H01L21/76—Making of isolation regions between components
  • H01L21/762—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers
  • H01L21/76224—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using trench refilling with dielectric materials
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10B—ELECTRONIC MEMORY DEVICES
  • H10B69/00—Erasable-and-programmable ROM [EPROM] devices not provided for in groups H10B41/00 - H10B63/00, e.g. ultraviolet erasable-and-programmable ROM [UVEPROM] devices
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10B—ELECTRONIC MEMORY DEVICES
  • H10B43/00—EEPROM devices comprising charge-trapping gate insulators
  • H10B43/30—EEPROM devices comprising charge-trapping gate insulators characterised by the memory core region

Definitions

• the invention relates to a memory cell array, ⁇ re memory cells are present in the region of a main face several of a semiconductor substrate in which the memory cell m in substantially parallel rows of memory cells are arranged, and are mutually iso profiled ⁇ in which adjacent memory cell rows by at least one isolation trench, wherein the memory cell array, at least a gate dielectric contains a material having Ladungstrager- traps,, and wherein the Speicherzel ⁇ lenz rush each comprise at least one doped region.
• the invention further relates to a method for producing a memory cell arrangement in which a plurality of memory cell rows are generated in the area of a main area of a semiconductor substrate and are isolated from one another.
• Memory cells are used in a wide range of technologies.
• the memory cells can be both read-only memories, which are referred to as ROM (Read Only Memory), and programmable memories, which are referred to as PROM (Programmable ROM).
• ROM Read Only Memory
• PROM Programmable ROM
• Memory cell arrangements on semiconductor substrates are distinguished by the fact that they allow random access to the information stored in them. They contain a large number of transistors. During the reading process,
• a generic memory cell arrangement has been proposed in DE-OS 195 10 042. This memory cell arrangement contains m rows of MOS transistors. The MOS transistors are connected in a row in each row. For ER- storage density hohung adjacent rows are respectively arranged from ⁇ partly on the ground of strip-shaped longitudinal trenches and Zvi ⁇ rule adjacent strip-shaped longitudinal trenches on the surface of the substrate. Interconnected source / dram areas are designed as a contiguous doped area. By activating it line by line, it is possible to read out this memory cell arrangement.
• the known memory cell arrangement is programmed during its manufacture. However, memory is required for many applications, m the data can be written in by electrical programming.
• electrically programmable memory cell arrangements information can be stored by a suitable configuration of MOS transistors.
• MOS transistors For example, it is possible for a so-called floating gate to be arranged between the gate and the channel region of a MOS transistor. Such a floating gate can be provided with an electrical charge. In this case, the operating voltage of the MOS transistor depends on the charge on the floating gate.
• This memory cell arrangement is characterized in that the space requirement of 4 required for the memory cells 3 F 2 was reduced to 2 F 2 , where F is the minimum structural width of the photolithographic process used for the production.
• F is the minimum structural width of the photolithographic process used for the production.
• FIG. 1 Another known memory cell arrangement is shown in US Pat. No. 5,306,941.
• bit lines are arranged in the edge region of memory row bars, the bit lines of adjacent memory cell bars facing one another.
• the bit lines are each separated from one another by an isolation trench filled with an insulating material.
• This document also discloses a method for producing a memory cell arrangement in which memory cell bridges are formed by etching isolation trenches in a semiconductor substrate. After etching the isolation trench, a dopant diffuses, bit lines being formed by the diffusion.
• a gate dielectric is also formed on and between the memory cell rows.
• This generic memory cell arrangement is suitable for structure sizes of at least 0.5 ⁇ m and for a ROM read-only memory. Electrical programming is not possible here.
• the object of the invention is to avoid the disadvantages of the prior art.
• a memory cell arrangement is to be created in which the largest possible number of memory cells can be arranged in the smallest possible space.
• this object is achieved in that a generic memory cell arrangement is designed in such a way that the memory cell rows are designed in the form of webs, the webs protruding beyond a level of the semiconductor substrate in that the memory cell rows are constructed in several parts and at least in their upper region a 4 bit contained in that said gate dielectric is disposed above the bit line that the gate dielectric a Mate ⁇ rial containing with charge carrier-traps that the isolati ⁇ onsgraben narrower than the bit line and m that the Isola- tion dig deeper, the semiconductor substrate penetrating than the bit line .
• the invention therefore provides for a memory cell arrangement with rows of memory cells to be configured such that the rows with the memory cells m in the form of webs protrude beyond a plane of the semiconductor substrate and are separated from one another by trenches.
• the trenches, or the other spaces between the rows of memory cells, are filled with an insulating material which also protrudes beyond the level of the semiconductor substrate.
• the memory cell arrangement is designed such that the isolation trench has a height of 50 nm to 200 nm.
• the generic method for producing the memory cell arrangement is carried out according to the invention in such a way that first areas of an etching mask are applied to the main surface of the semiconductor substrate, and then on the edges of the
• Areas of the spacer are generated so that after the creation of the spacer between the first areas, second areas of the etching mask are formed and that a later process step causes the spacing pieces to be etched selectively to the first areas and the second areas of the etching mask.
• the spacers are produced in that a cover layer is deposited on the first regions of the etching mask and on regions of the semiconductor substrate not covered by the first regions of the etching mask and then 5 areas of the cover layer, which extend parallel to the main surface of the semiconductor substrate, are etched away.
• Memory cell rows are preferably produced in such a way that the first areas of the etching mask are produced as essentially parallel webs.
• the second regions of the etching mask are produced in such a way that they form essentially parallel webs.
• FIG. 1 shows a top view of a memory cell arrangement in which adjacent rows of memory cells are insulated from one another by insulating trenches
• FIG. 2 shows a cross section through the semiconductor substrate along line VII-VII shown in FIG. 1 after application of first areas of an etching mask
• FIG. 3 shows the semiconductor substrate shown in FIG. 2 after application of a layer
• FIG. 4 shows the semiconductor substrate shown in FIG. 3 after the layer has been etched away, with the exception of spacers on the first regions and application of second regions of the etching mask,
• FIG. 5 shows a cross section through the semiconductor substrate along the line VII-VII with an etching mask located on the semiconductor substrate after the spacers and
• FIG. 6 shows a cross section through the semiconductor substrate along the line VII-VII after etching the isolation trench, removing the etching mask and filling the
• FIG. 7 shows a cross section through the semiconductor substrate along the line VII-VII after application of a dielectric multiple layer and growth of a first electrode layer
• FIG. 8 shows a cross section through the semiconductor substrate along line VIII-VIII shown in FIGS . 1 and 7 after structuring the first electrode layer and depositing a further insulating material
• FIG. 11 shows a cross section through the semiconductor substrate along the line VIII-VIII after growth of a dielectric layer and deposition of a second electrode layer
• FIG. 12 shows a cross section through the semiconductor substrate along the line VIII-VIII after structuring the second electrode layer
• FIG. 13 shows a plan view of a section of the semiconductor substrate after forming contacts to the structured electrode layers which act as gate electrodes,
• FIG. 1 shows a top view of a memory cell arrangement with first word lines WL 1 and second word lines WL 2, which are arranged alternately.
• the distance between adjacent word lines WL 1 and WL 2 is less than the width of the word lines WL 1, WL 2.
• Bit lines BL each having a first doped region D 1 and a second doped region, run across the word lines WL 1, WL 2 D 2 have.
• the memory cell Assembly further contains a gate dielectric and gate electrode ⁇ .
• the bit lines BL are each arranged in an upper region of webs.
• the individual bit lines BL are isolated from each other by ⁇ isolation trench (trench) T.
• the isolation trenches T are considerably narrower than the bit lines BL and have a thickness of 10 nm to 100 nm, preferably 30 to 60 nm, the exemplary embodiment shown here relating to a width of the isolation trenches T of approximately 50 nm.
• the distance between the centers of adjacent first word lines WL 1 and second word lines WL 2 is chosen to be as small as possible and preferably corresponds to the minimum structure size F of the manufacturing process of the memory cell arrangement.
• the distance between the centers of adjacent bit lines BL is also preferably a minimum structure size F.
• the space requirement per memory cell which is defined as an intersection of one of the word lines WL 1, WL 2 and one of the bit lines BL, is 1 F.
• bit selection lines BA0, BAI and BA2 running transverse to the bit lines BL.
• bit lines BL - three in the illustrated case - are combined to form nodes K, K via a metallization (not shown), which is preferably arranged in a higher structural level.
• bit selection lines BA0, BAI and BA2 are arranged between the node K and the second doped region D 2 as bit lines BL m are brought together in the node K.
• Selection transistors AT of the decoder can be controlled via the bit selection lines BA.
• the selection transistors AT are 9 are located at individual intersections of the bit selection lines BA with the bit lines BL. In this case, one crossing point is provided with a selection transistor AT per bit line BL.
• Channel doping is provided at points of intersection of the bit selection lines BA with the bit lines BL, at which no selection transistors AT are arranged.
• the channel doping creates a parasitic MOS transistor at each of these crossing points, which has a threshold voltage which is so high that it conducts independently of a level applied to a corresponding bit selection line BA. This threshold voltage is preferably negative.
• This memory cell arrangement is preferably produced in the manner shown below:
• Dopant such as boron of preferably 1 x 10 ' cm “1 to 1 x 10 1C cm " ⁇ for example 2 x 10 15 cm ⁇ % is a p-doped trough 15 with a dopant concentration of, for example, 1 x 10 1 ' cm -3 Implantation formed.
• the depth of the p-doped well 15 is, for example, approximately 1 ⁇ m.
• first areas of a mask are applied.
• the first regions of the mask are in the form of parallel webs 20 which extend over one of the main surfaces of the semiconductor substrate 10.
• the webs 20 have a width which essentially corresponds to a minimally producible structure size F.
• F is preferably in the range from 0.1 ⁇ m to 0.5 ⁇ m. This processing state of the semiconductor substrate is shown in FIG. 2.
• the first areas of the mask consist, for example, of a TEOS (Si (OC 2 H 5 )) -
• the TEOS process is preferably carried out in such a way that tetraethyl ortho 10 Silicate Si (OC H) 4 is converted at a temperature of about 700 U C and a pressure in the range of about 40 Pa silicon oxide.
• a cover layer 30 is applied conformally to the semiconductor substrate processed in this way (see FIG. 3).
• the applied cover layer 30 consists, for example, of silicon nitride Si 4 .
• the thickness of the cover layer 30 is preferably 5 nm to 50 nm, a thickness in the range of 20 nm being preferred.
• the cover layer 30 is preferably applied by a CVD (Chemical Vapor Deposition) process, in particular by an LPCVD (Low Pressure CVD) process.
• CVD Chemical Vapor Deposition
• LPCVD Low Pressure CVD
• LPCVD process is characterized in that dichlorosilane (S ⁇ H 2 CL) with the addition of ammonia (NH at a temperature in the range of about 750 ° C m a plasma at a pressure between 10 Pa and 100 Pa, preferably 30 Pa, m silicon nitride (S ⁇ ⁇ N 4 ) is converted.
• the top layer is then etched away 30 m areas which extend parallel to a main surface of the semiconductor substrate 10 by an anisotropic dry etching process.
• the cover layer 30 on the upper surface of the webs 20 and in the bottom region of the trench 40 is removed.
• the cover layer 30 is removed with an etchant which selectively etches the cover layer 30 to the material of the webs 20 and to the semiconductor substrate 10.
• a cover layer 30 consisting of S ⁇ ⁇ N 4 , which is based on webs 20 made of SiO ⁇ . and is located on a surface of the semiconductor substrate 10, is particularly suitable as an etchant for such a selective etching CHF.
• the etching process takes place until the cover layer 30 on the upper surfaces of the webs 20 and in the region of the bottom of the trench 40 has been completely removed. This means that 11 stand 20 spacers 50 in the side region of the webs.
• the spacers 50 have a width of approximately 50 nm. This requires a thickness of the cover layer 30 of 50 nm.
• a material 60 is deposited, which preferably has the same chemical composition as the first areas of the etching mask.
• the material 60 is applied so thick that it fills the trenches 40 as much as possible.
• the method is expediently carried out in such a way that all regions of the trenches 40 are filled with the material 60 up to a line 70.
• This processing state of the semiconductor substrate is shown in FIG. 4.
• the structure thus created is then planarized with a suitable planarization process, for example by chemical mechanical polishing (CMP), so that only areas reaching up to line 70 remain.
• CMP chemical mechanical polishing
• the spacers 50 are removed by selective etching, for example with phosphoric acid, at a preferably elevated temperature.
• Concentrated phosphoric acid has a particularly high selectivity for a nitride layer. In principle, it is possible to have the etching process take place at room temperature, but it is more sensible to accelerate the etching process by carrying it out at an elevated temperature. It is particularly expedient to carry out the etching process at a temperature in the range of approximately 160.degree.
• an etching process is carried out, for example in several stages via a first etching step with a gas mixture of CF, and 0 : or CHF ⁇ and 0? and carried out with a HBr-containing gas via a second etching step, so that insulation trenches 85 form in the semiconductor substrate 10 below the locations at which the spacers 50 were in a previous process step.
• the isolation trenches 85 are identified with the reference symbol T in the top view in FIG. 1.
• the isolation trenches 85 have a depth of 20 nm to 200 nm, 100 nm being a particularly preferred value.
• the isolation trenches 85 are preferably about 5 times as deep as they are wide.
• the isolation trenches 85 are then filled with an insulation material.
• SiO is particularly suitable as a full material.
• a planarization process takes place, preferably a process of chemical-mechanical planning. The processing state of the semiconductor substrate achieved in this way is shown in FIG. 6.
• bit lines 86 are produced by implanting the semiconductor substrate 10 up to a line 82 in a dopant, for example boron.
• the dopant is of the same conductivity type as that 13 dopant in the area of the tub 15.
• bit lines 86 for example, 1 x 10 1 "cm -3 to channel regions form of transistors having ei ⁇ ne threshold voltage of typically 0.5V.
• EmsatzHarsimplantation The implantation process takes place, for example, with a dose of 3 x 10 cm " and an energy of 25 keV (not shown).
• bil to len ⁇ between the isolation trench 85 Speicherzellenzei ⁇ have the shape of ridges projecting beyond the semiconductor substrate 10.
• a programming mask is formed, for example, egg ⁇ nem photoresist by photolithographic process steps ge ⁇ .
• n-doping ions for example As with a dose of 1 x 10 14 cm " and one
• Channel doping is generated at those points of intersection of the bit selection lines BA with the bit lines BL at which no selection transistors AT are formed.
• a suitable dielectric layer is applied to the bit lines 86 and the isolation trenches 85.
• the dielectric layer can preferably be formed by a multilayer. It is particularly expedient if the dielectric layer is a triple layer with a first dielectric layer 90 made of silicon oxide Si 2 mm with a thickness of approximately 3 nm, a central dielectric layer 100 made of silicon nitride with a thickness of approximately 7 to 8 nm and an upper dielectric layer 110 made of silicon oxide with a thickness of approximately 4 nm. Such a sequence of the thicknesses of the layers is particularly expedient in order to store captured charges as long as possible.
• the first dielectric layer 90 is, for example, tempered in an atmosphere containing 0 and in a 14 desired layer thickness was formed.
• the silicon of the webs 30 m silicon oxide S ⁇ 0 2 is converted.
• the second dielectric layer 100 is preferably applied by a CVD (Chemical Vapor Deposition) process, in particular by an LPCVD (Low Pressure CVD) process.
• CVD Chemical Vapor Deposition
• LPCVD Low Pressure CVD
• a particularly suitable variant for forming the second dielectric layer 100 according to the LPCVD method can be achieved in that dichlorosilane (S1H2CL) with the addition of ammonia (NH) at a temperature in the range of approximately 750
• Si ⁇ N 4 silicon nitride
• the upper dielectric layer 110 is then deposited by thermal oxidation, preferably in an HO-containing atmosphere at a temperature around 900 ° C. and for a period of about 2 hours, or by one of the known layer production processes, for example an HTO process.
• a deposition using an HTO process can preferably be carried out by converting dichlorosilane SiH Cl in a nitrogen-containing atmosphere at a temperature of approximately 900 ° C. and a pressure in the range of 40 Pa m silicon oxide SiO.
• a first electrode layer 120 for example made of highly doped polycrystalline silicon, is grown on the upper dielectric layer 110.
• a preferred doping of the low-poly silicon is at least 10 20 cm “ , doping from 10 21 cm “ 1 being particularly suitable.
• the first electrode layer 120 can also be formed from a metal silicide and / or a metal.
• the first electrode layer 120 is doped by situ-doped deposition or undoped deposition and subsequent implantation or diffusion of a dopant.
• An n + doping is preferably carried out, for example with phosphorus or arsenic.
• the electrode layer 120 can 15, however, can also be p -doped.
• An implantation is carried out, for example, with an energy of 80 keV and a dose of 1 x 10 16 cm "This processing state of the semiconductor substrate m Figure 7 is illustrated Figure 7 is the same as the Figures 2 to 6 em cross-section along the line VII - VII. M Figure 1.
• a paint mask is then applied to the first electrode layer 120.
• This is followed by an etching process, for example in several stages with a first etching step with a gas mixture of CF 4 and 0 2 or CHF, and 0 2 and a second etching step with a HBr-containing gas.
• the first electrode layer 120 is etched trench 130 m.
• the remaining material of the first electrode layer 120 creates webs 140 between the trenches 130, which serve as word lines for the finished memory cell arrangement.
• Other bit selection lines not shown for reasons of space, run parallel to the webs 140 and are preferably produced in the same way as the word lines.
• the coating mask can also be transferred via a previously deposited layer, in particular a tetraethyl orthosilicate (TEOS) layer.
• TEOS tetraethyl orthosilicate
• An insulation layer 150 is then deposited on the webs 140 and the trenches 130 using a suitable method which is as conformable as possible. It is particularly expedient to form the insulation layer 150 using a TEOS method. This can be done by converting tetraethyl orthosilicate Si (OC 2 H 5 ) at a temperature of approximately 700 ° C. and a pressure in the range of 40 Pa m silicon oxide SiO.
• FIG. Figure 8 shows one 16 Section perpendicular to the cross sections shown in FIGS. 2 to 7 along the line XIII-XIII marked in FIGS. 1 and 7.
• etching process the nitride-containing dielectric layer 100 being removed by using a suitable agent, for example phosphoric acid with a concentration in the range of 80% and a temperature around 150 ° C.
• a suitable agent for example phosphoric acid with a concentration in the range of 80% and a temperature around 150 ° C.
• the multi-stage etching process stops on the oxide-containing lower dielectric layer 90.
• the thin dielectric layer 90 is removed in the area of the trench 130 by a further etching process, for example using a solution containing HF (HF-dip). This state of the semiconductor substrate is shown in FIG. 10.
• a sacrificial layer (a so-called sacrificial oxide), for example made of silicon oxide, is then grown and etched with hydrofluoric acid (not shown).
• a further dielectric layer is then deposited.
• the further dielectric layer preferably has the same structure as the dielectric layer previously removed in the trench 130.
• the dielectric layer is preferably formed by a multilayer. It is particularly expedient if the further dielectric layer is a triple layer.
• the triple layer is expediently deposited in such a way that the first dielectric layer 90 made of silicon oxide SiO m of a dic- 17 ke of about 3 nm, the middle dielectric layer are formed of silicon nitride 100 nm newly of about 7 to 8 nm thickness and obe ⁇ re dielectric layer 110 of silicon oxide having a thickness of about 4 hours.
• This deposition process forms a lower dielectric layer 180, a middle dielectric layer 190 and an upper dielectric layer 200 on the webs 140.
• the lower dielectric layer 180 preferably consists of silicon oxide Si0 2 , which is formed, for example, in an annealing process in a desired layer thickness.
• 120 silicon is converted into an oxygen-containing atmosphere at a temperature of approximately 800 to 900 ° C. silicon oxide Si0 2 .
• the middle dielectric layer 190 is preferably formed by a nitride layer produced by the LPCVD process at approximately 700 ° C.
• the uppermost dielectric layer 200 preferably consists of the same material as the lower dielectric layer 180, that is again preferably of Si0 2 .
• the thickness of the lower dielectric layer 180 is, for example, 3 nm
• the thickness of the middle dielectric layer 190 is approximately 7 to 8 nm
• the thickness of the upper dielectric layer 200 is 4 nm.
• the application of the lower dielectric layer 180 increases the lateral extent of the spacers 160, vertical regions of the layers 190 and 200 also remaining on the spacers 160.
• a second electrode layer 210 is then formed over the entire surface.
• the second electrode layer 210 consists, for example, of a doped semiconductor material, preferably n-doped low-poly silicon, a metal silicide and / or a metal. This state of the semiconductor substrate is shown in FIG. 11. 18
• the semiconductor material of the second electrode layer 210 can, however, also be p-doped.
• the second electrode layer 210 is formed with a thickness that is sufficient to fill the trenches 130 between the webs 140.
• the second electrode layer 210 is therefore deposited in a thickness of approximately 0.2 ⁇ m to 0.6 ⁇ m, preferably 0.4 ⁇ m.
• the second electrode layer 210 is then structured.
• the second word lines WL2 are then formed by structuring the second electrode layer 210.
• the first word lines, designated WL 1 in FIG. 1, are formed by the webs 140.
• the second electrode layer 210 is structured using a multi-layer method. First, the upper area of the second electrode layer 210 is removed by a planarizing process, for example a CMP step.
• the middle dielectric layer 190 acts as a stop layer.
• CMP chemical mechanical planarizing
• the first word lines WL1 and the second word lines WL2 are structured in such a way that they have word line widenings WLA, on which word line contacts WLK are formed to aluminum tracks AL running transversely thereto (see FIG. 13).
• the word lines WL1, WL2 are formed such that they are widened on one side in the area of the word line contact WLK.
• the word line widening WLA arises from the fact that these one-sided widenings each on opposite 19 sides of the word line WL1, WL2 are arranged. Before and out ⁇ ter the word line WLA widening the width of the word line WL1, WL2 is lower than in the region of the word line WLA expansion.
• the word line WLA widenings of benachbar ⁇ th word lines WL1, WL2 are arranged offset from one another.
• the width of the word lines WL1, WL2 outside the word line widenings WLA is approximately half the value in the area of the word line widenings WLA. In this way, a secure opening of contact holes to form the word line contacts WLK is ensured without increasing the space requirement of the word lines too much.
• the word line widenings WLA cause an additional space requirement m direction of the width of the word lines WL1, WL2 of approximately one word line per segment over the entire cell field. For example, a segment comprises 32 to 128 word lines.
• the memory cell arrangement is completed by the deposition of an intermediate oxide, contact hole etching, application and structuring of a metal layer. These known process steps are not shown.
• the memory cell arrangement shown is preferably operated with a programming voltage of approximately 12 V, the voltage occurring between adjacent bit lines corresponding approximately to half the programming voltage, that is to say 6 V here.
• a programming voltage of approximately 12 V
• the voltage occurring between adjacent bit lines corresponding approximately to half the programming voltage, that is to say 6 V here.
• Such a voltage between adjacent bit lines is sufficiently ensured by a depth of the isolation trenches 85 of approximately 100 nm to several 100 nm.

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• 1999
  • 1999-03-23 EP EP99923389.3A patent/EP1068645B1/de not_active Expired - Lifetime
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